Corrected QT (QTc)
Also calledQTc · corrected QT interval · rate-corrected QT
Definition
The QT interval corrected for heart rate. The most widely used correction is the Bazett formula, which divides the measured QT by the square root of the RR interval in seconds (QTc = QT divided by the square root of RR). The 2009 AHA/ACCF/HRS recommendations regard a QTc of 450 ms or longer in men and 460 ms or longer in women as prolonged, and 390 ms or shorter as short. A QTc above 500 ms is associated with a 2- to 3-fold higher risk of torsades de pointes. Under the 2022 ESC criteria, short QT syndrome is diagnosed with a QTc of 320 ms or less on its own, or 360 ms or less together with a family history of short QT syndrome, survived cardiac arrest without heart disease, or a disease-causing gene variant.
Clinical noteBazett tends to give overlong QTc values at fast heart rates, particularly above 85 bpm, and is less reliable below 60 bpm or above 90 bpm, so QTc can mislead at heart-rate extremes. Short-QT cutoffs differ between sources: 390 ms or less in the 2009 AHA/ACCF/HRS statement, but 320 ms or less (or 360 ms or less with supporting findings) for the 2022 ESC diagnosis of short QT syndrome.
Sources
- Rautaharju PM, Surawicz B, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval. Circulation. 2009;119(10):e241-e250. doi.org/10.1161/CIRCULATIONAHA.108.191096
- Drew BJ, Ackerman MJ, Funk M, et al. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. Circulation. 2010;121(8):1047-1060. doi.org/10.1161/CIRCULATIONAHA.109.192704
- Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J. 2022;43(40):3997-4126. doi.org/10.1093/eurheartj/ehac262
- Samesima N, God EG, Kruse JCL, et al. Brazilian Society of Cardiology guidelines on the analysis and issuance of electrocardiographic reports - 2022. Arq Bras Cardiol. 2022;119(4):638-680. doi.org/10.36660/abc.20220623
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.